1361087 - Loading osfile_shared_allthreads.jsm does main thread IO on Windows

Status: RESOLVED FIXED

(Toolkit :: OS.File, defect, P1)

Description

[Florian Quèze [:florian]]

See this profile: https://perfht.ml/2p1uyD1

Loading osfile_shared_allthreads.jsm (which is done during early startup) initializes the OSFileConstantsService at http://searchfox.org/mozilla-central/rev/3dc6ceb42746ab40f1441e1e659ffb8f62ae78e3/toolkit/components/osfile/modules/osfile_shared_allthreads.jsm#94

This creates the nsSystemInfo service at http://searchfox.org/mozilla-central/rev/3dc6ceb42746ab40f1441e1e659ffb8f62ae78e3/dom/system/OSFileConstants.cpp#326

And in the profile linked above, this spends 276ms of startup time doing main thread IO in a gethostname call (we don't seem to use this information).

I think some of this should be lazy-ified, if not completely ifdef'ed out on Windows, as this comment makes me think this has very little value there:
  // Get the umask from the system-info service.
  // The property will always be present, but it will be zero on
  // non-Unix systems.

Comment 1

[David Teller [:Yoric] - still alive but not very active]

#ifdef-ing it away on Windows definitely makes sense.

I think that we could replace this directly with `nsSystemInfo::gUserMask`, which shouldnt' need to initialize the nsSystemInfo service.

Comment 2

[Florian Quèze [:florian]]

Attachment: Patch

Comment 3

[(no longer active)]

We sort of have the same bug in the download manager too!

<http://searchfox.org/mozilla-central/rev/ae8c2e2354db652950fe0ec16983360c21857f2a/toolkit/components/downloads/nsDownloadManager.cpp#3381>

Comment 4

[Florian Quèze [:florian]]

(In reply to :Ehsan Akhgari (super long backlog, slow to respond) from comment #3)
> We sort of have the same bug in the download manager too!
> 
> <http://searchfox.org/mozilla-central/rev/
> ae8c2e2354db652950fe0ec16983360c21857f2a/toolkit/components/downloads/
> nsDownloadManager.cpp#3381>

Hopefully that download manager code doesn't run during early startup, so I don't think we really need to apply the fix there. Especially if bug 1361495 gets fixed.

Comment 5

[David Teller [:Yoric] - still alive but not very active]

Comment on attachment 8863871 [details] [diff] [review]
Patch

Review of attachment 8863871 [details] [diff] [review]:
-----------------------------------------------------------------

::: dom/system/OSFileConstants.cpp
@@ +326,5 @@
>  
>    // Get the umask from the system-info service.
>    // The property will always be present, but it will be zero on
>    // non-Unix systems.
> +  // It's initialized before nsSystemInfo::Init, so we don't need to

Nit: instead of "It", writing `nsSystemInfo::gUserMask` might be clearer.

Also, the important part is that `nsSystemInfo::gUserMask` is already initialized, by `NS_InitXPCOM2` (iirc).

Comment 6

[Florian Quèze [:florian]]

Try looks green enough: https://treeherder.mozilla.org/#/jobs?repo=try&revision=a62a0c2dc743f8d7f36bf877b9acaa8164a00b99

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/427d001e5539
Loading osfile_shared_allthreads.jsm should not initialize the system-info service (as it does main thread IO on Windows), r=Yoric.

Comment 8

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/427d001e5539

Comment 9

[Marco Bonardo [:mak]]

(In reply to :Ehsan Akhgari (super long backlog, slow to respond) from comment #3)
> We sort of have the same bug in the download manager too!
> 
> <http://searchfox.org/mozilla-central/rev/
> ae8c2e2354db652950fe0ec16983360c21857f2a/toolkit/components/downloads/
> nsDownloadManager.cpp#3381>

That code is no more used in Firefox, we now use jsdownloads.

Comment 10

[:Paolo Amadini]

...and now it's time to tackle bug 851471 and dependencies, as this unused code comes up all the time. I'll see what I can do today.